U.S. patent application number 10/830264 was filed with the patent office on 2004-10-07 for magnetic element with insulating veils and fabricating method thereof.
Invention is credited to Chen, Eugene Youjun, DeHerrera, Mark, Durlam, Mark, Kerszykowski, Gloria, Kyler, Kelly Wayne, Tehrani, Saied N..
Application Number | 20040197579 10/830264 |
Document ID | / |
Family ID | 24239151 |
Filed Date | 2004-10-07 |
United States Patent
Application |
20040197579 |
Kind Code |
A1 |
Chen, Eugene Youjun ; et
al. |
October 7, 2004 |
Magnetic element with insulating veils and fabricating method
thereof
Abstract
An improved and novel device and fabrication method for a
magnetic element, and more particularly a magnetic element (10)
including a first electrode (14), a second electrode (18) and a
spacer layer (16). The first electrode (14) and the second
electrode (18) include ferromagnetic layers (26 & 28). A spacer
layer (16) is located between the ferromagnetic layer (26) of the
first electrode (14) and the ferromagnetic layer (28) of the second
electrode (16) for permitting tunneling current in a direction
generally perpendicular to the ferromagnetic layers (26 & 28).
The device includes insulative veils (34) characterized as
electrically isolating the first electrode (14) and the second
electrode (18), the insulative veils (34) including non-magnetic
and insulating dielectric properties. Additionally disclosed is a
method of fabricating the magnetic element (10) with insulative
veils (34) that have been transformed from having conductive
properties to insulative properties through oxygen plasma ashing
techniques.
Inventors: |
Chen, Eugene Youjun;
(Gilbert, AZ) ; Durlam, Mark; (Chandler, AZ)
; Tehrani, Saied N.; (Tempe, AZ) ; DeHerrera,
Mark; (Tempe, AZ) ; Kerszykowski, Gloria;
(Fountain Hills, AZ) ; Kyler, Kelly Wayne; (Mesa,
AZ) |
Correspondence
Address: |
INGRASSIA FISHER & LORENZ, P.C.
7150 E. CAMELBACK, STE. 325
SCOTTSDALE
AZ
85251
US
|
Family ID: |
24239151 |
Appl. No.: |
10/830264 |
Filed: |
April 21, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10830264 |
Apr 21, 2004 |
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10349702 |
Jan 22, 2003 |
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10349702 |
Jan 22, 2003 |
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09560738 |
Apr 28, 2000 |
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Current U.S.
Class: |
428/469 ;
427/127 |
Current CPC
Class: |
Y10T 29/49052 20150115;
Y10T 29/49044 20150115; H01L 43/12 20130101; Y10T 428/24917
20150115; B82Y 40/00 20130101; H01F 10/324 20130101; B82Y 25/00
20130101; H01F 41/302 20130101; Y10T 29/49046 20150115 |
Class at
Publication: |
428/469 ;
427/127 |
International
Class: |
B05D 005/12; B32B
009/00 |
Claims
1. A magnetic element comprising: a first electrode including a
ferromagnetic layer; a second electrode positioned spaced apart
from the first electrode, the second electrode including a
ferromagnetic layer; a spacer layer located between the
ferromagnetic layer of the first electrode and the ferromagnetic
layer of the second electrode; and an insulative veil defining the
magnetic element, wherein the insulative veil is characterized as
electrically isolating the first electrode and the second
electrode.
2. A magnetic element as claimed in claim 1 wherein the
ferromagnetic layers of the first electrode and the second
electrode include in combination a fixed ferromagnetic layer and a
free ferromagnetic layer, the fixed ferromagnetic layer having a
magnetization that is fixed in a preferred direction in the
presence of an applied magnetic field capable of switching the free
layer, and the free ferromagnetic layer having a magnetization that
is free to rotate between magnetization states in the presence of
an applied magnetic field.
3. A magnetic element as claimed in claim 1 wherein the free
ferromagnetic layer and the fixed ferromagnetic layer include at
least one of NiFe, NiFeCo, CoFe, or Co.
4. A magnetic element as claimed in claim 1 wherein the
ferromagnetic layers of the first electrode and the second
electrode include a first switching field and a second switching
field thereby defining a pseudo spin-valve structure.
5. A magnetic element as claimed in claim 1 wherein the insulative
veil is formed of an inactive material.
6. A magnetic element as claimed in claim 5 wherein the insulative
veil is formed of a dielectric material.
7. A magnetic element as claimed in claim 1 wherein the spacer
layer includes one of a dielectric material defining a MTJ
structure or a conductive material defining a spin valve
structure.
8-17 (canceled)
Description
FIELD OF THE INVENTION
[0001] The present invention relates to magnetic elements for
information storage and/or sensing and a fabricating method
thereof, and more particularly, to a device and method of
fabricating the magnetic element to include insulative veils.
BACKGROUND OF THE INVENTION
[0002] This application is related to a co-pending application that
bears Motorola docket number CR97-133 and U.S. Ser. No. 09/144,686,
entitled "MAGNETIC RANDOM ACCESS MEMORY AND FABRICATING METHOD
THEREOF," filed on Aug. 31, 1998, assigned to the same assignee and
incorporated herein by this reference, co-pending application that
bears Motorola docket number CR 97-158 and U.S. Ser. No.
08/986,764, entitled "PROCESS OF PATTERNING MAGNETIC FILMS" filed
on Dec. 8, 1997, assigned to the same assignee and incorporated
herein by this reference and issued U.S. Pat. No. 5,768,181,
entitled "MAGNETIC DEVICE HAVING MULT-LAYER WITH INSULATING AND
CONDUCTIVE LAYERS", issued Jun. 16, 1998, assigned to the same
assignee and incorporated herein by.
[0003] Typically, a magnetic element, such as a magnetic memory
element, has a structure that includes ferromagnetic layers
separated by a non-magnetic layer. Information is stored as
directions of magnetization vectors in magnetic layers. Magnetic
vectors in one magnetic layer, for instance, are magnetically fixed
or pinned, while the magnetization direction of the other magnetic
layer is free to switch between the same and opposite directions
that are called "parallel" and "anti-parallel" states,
respectively. In response to parallel and anti-parallel states, the
magnetic memory element represents two different resistances. The
resistance has minimum and maximum values when the magnetization
vectors of the two magnetic layers point in substantially the same
and opposite directions, respectively. Accordingly, a detection of
change in resistance allows a device, such as an MRAM device, to
provide information stored in the magnetic memory element. The
difference between the minimum and maximum resistance values,
divided by the minimum resistance is known as the magnetoresistance
ratio (MR).
[0004] An MRAM device integrates magnetic elements, more
particularly magnetic memory elements, and other circuits, for
example, a control circuit for magnetic memory elements,
comparators for detecting states in a magnetic memory element,
input/output circuits, etc. These circuits are fabricated in the
process of CMOS (complementary metal-oxide semiconductor)
technology in order to lower the power consumption of the
device.
[0005] During typical magnetic element fabrication, such as MRAM
element fabrication, metal films are grown by sputter deposition,
evaporation, or epitaxy techniques. One such magnetic element
structure includes a substrate, a base electrode multilayer stack,
a synthetic antiferromagnetic (SAF) structure, an insulating tunnel
barrier layer, and a top electrode stack. The base electrode layer
stack is formed on the substrate and includes a first seed layer
deposited on the substrate, a template layer formed on the seed
layer, a layer of an antiferromagnetic material on the template
layer and a pinned ferromagnetic layer formed on and exchange
coupled with the underlying antiferromagnetic layer. The
ferromagnetic layer is called the pinned layer because its magnetic
moment (magnetization direction) is prevented from rotation in the
presence of an applied magnetic field. The SAF structure includes a
pinned ferromagnetic layer, and a fixed ferromagnetic layer,
separated by a layer of ruthenium, or the like. The top electrode
stack includes a free ferromagnetic layer and a protective layer
formed on the free layer. The magnetic moment of the free
ferromagnetic layer is not pinned by exchange coupling, and is thus
free to rotate in the presence of applied magnetic fields.
[0006] During fabrication of these magnetic elements, ion milling
is commonly used for the dry etching of the magnetic materials.
However, during the process of dry etching, conducting veils are
left remaining on the sides of the magnetic tunnel junction (MTJ).
These remaining veils lead to electrical shorting of the device
between the bottom and top electrodes, more particularly across the
insulating tunnel barrier. Currently, wet etching techniques are
used in the semiconductor industry to etch away the veils, but are
not amenable for use in conjunction with magnetic materials due to
their chemical attack on the magnetic materials leading to device
performance degradation.
[0007] To avoid the shorting problem caused by veils, the current
etching process is done in two steps. First the top magnetic layer
of the magnetic element is etched or defined, then the whole stack
is etched using a dry etch technique; or vice versa. Veils may be
minimized by varying the etching beam angle relative to the wafer
surface. Since the edges of the top and bottom magnetic layers do
not overlap, the veils do not cause a shorting problem between the
top and bottom magnetic layers. However, this is a very complex
etching process. Stopping the etch of the top magnetic layer
without over-etching through the ultra thin tunnel barrier, and
into the bottom magnetic layer is very difficult to do.
Over-etching into the bottom magnetic layer will cause unwanted
magnetic poles shifting the resistance-magnetic field response of
the magnetic element. This technique also limits the free magnetic
layer to be placed on top of the tunnel barrier.
[0008] Accordingly, it is a purpose of the present invention to
provide for a magnetic element having formed as a part thereof,
insulating veils, which no longer include conductive or magnetic
properties.
[0009] It is a still further purpose of the present invention to
provide a method of forming a magnetic element with insulating
veils.
[0010] It is another purpose of the present invention to provide a
method of fabricating a magnetic element that includes plasma
oxygen ashing of the magnetic stack to transform conducting veils
into insulating veils.
[0011] It is another purpose of the present invention to provide a
method of forming a magnetic element with insulating veils which is
amenable to simple and high throughput manufacturing.
[0012] It is still a further purpose of the present invention to
provide a method of forming a magnetic element with insulating
veils that allows for the formation of the free magnetic layer
anywhere within the magnetic element stack.
SUMMARY OF THE INVENTION
[0013] These needs and others are substantially met through
provision of a magnetic element including a base metal layer, a
first electrode, a second electrode and a spacer layer. The base
metal layer is positioned on an uppermost surface of a substrate
element. A spacer layer is located between the ferromagnetic layers
for permitting tunneling current in a direction generally
perpendicular to the ferromagnetic layers. In an alternative
embodiment, the structure is described as including a SAF structure
to allow for proper balancing of magnetostatic interaction in the
magnetic element. The device includes insulative veils
characterized as electrically isolating the first electrode and the
second electrode, the insulative veils including non-magnetic and
insulating dielectric properties. Additionally disclosed is a
method of fabricating the magnetic element with insulative veils
that have been transformed from having conductive properties to
having insulative properties through oxygen plasma ashing
techniques.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIGS. 1-3 illustrate in cross-sectional views, the steps in
fabricating a magnetic element with insulative veils according to
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] During the course of this description, like numbers are used
to identify like elements according to the different figures that
illustrate the invention. FIGS. 1-3 illustrate in cross-sectional
views a magnetic element according to the present invention. More
particularly, illustrated in FIG. 1, is a first step in the
fabrication of a patterned magnetic element 10. Illustrated in FIG.
1, is a fully patterned magnetic element structure 10. The
structure includes a substrate 12, a first electrode multilayer
stack 14, a spacer layer 16 including oxidized aluminum, and a
second electrode multilayer stack 18. It should be understood that
spacer layer 16 is formed dependent upon the type of magnetic
element being fabricated. More particularly, in a MTJ structure,
spacer layer 16 is formed of a dielectric material, and in a spin
valve structure, spacer layer 16 is formed of a conductive
material. First electrode multilayer stack 14 and second electrode
multilayer stack 18 include ferromagnetic layers. First electrode
layers 14 are formed on a base metal layer 13, which is formed on
substrate 12. Base metal layer 13 is disclosed as composed of a
single metal material or layer or a stack of more than one metal
material or layer. First electrode layer 14 includes a first seed
layer 20, deposited on base metal layer 13, a template layer 22, a
layer of antiferromagnetic pinning material 24, and a fixed
ferromagnetic layer 26 formed on and exchange coupled with the
underlying antiferromagnetic pinning layer 24. It should be
understood that anticipated by this disclosure is a pseudo
spin-valve structure that would not include the antiferromagnetic
pinning layer. In this instance, the pseudo spin-valve structure
would include a first electrode and a second electrode including a
first switching field and a second switching field thereby defining
the pseudo spin-valve structure.
[0016] Typically, seed layer 20 is formed of tantalum nitride
(TaNx) having template layer 22 formed thereon. Template layer 22
in this particular embodiment is formed of ruthenium (Ru). Pinning
layer 24 is typically formed of iridium manganese (IrMn).
[0017] In this particular embodiment, ferromagnetic layer 26 is
described as fixed, or pinned, in that its magnetic moment is
prevented from rotation in the presence of an applied magnetic
field. Ferromagnetic layer 26 is typically formed of alloys of one
or more of the following: nickel (Ni), iron (Fe), and cobalt
(Co).
[0018] Second electrode stack 18 includes a free ferromagnetic
layer 28 and a protective contact layer 30. The magnetic moment of
the free ferromagnetic layer 28 is not fixed, or pinned, by
exchange coupling, and is free to rotate in the presence of an
applied magnetic field. Free ferromagnetic layer 28 is typically
formed of a nickel iron (NiFe) alloy or a nickel iron cobalt
(NiFeCo) alloy. It should be understood that a reversed, or
flipped, structure is anticipated by this disclosure. More
particularly, it is anticipated that the disclosed magnetic element
can be formed to include a top fixed, or pinned layer, and thus
described as a top pinned structure. In addition, a device
including dual spacer layers is anticipated by this structure. In
this instance, magnetic element 10 would structurally include a
bottom pinned magnetic layer, a bottom spacer, or tunnel barrier
layer, a free magnetic layer, a top spacer, or tunnel barrier
layer, and a top pinned magnetic layer. The bottom pinned magnetic
layer, the free magnetic layer and the top pinned magnetic layer
include ferromagnetic layers. The bottom magnetic layer is
optionally formed on a diffusion barrier layer which is formed on a
metal lead which in turn is typically formed on some type of
dielectric material. The diffusion barrier layer is typically
formed of tantalum nitride (TaN), and aids in the thermal stability
of the magnetic element.
[0019] Fixed ferromagnetic layer 26 is described as pinned, or
fixed, in that its magnetic moment is prevented from rotation in
the presence of an applied magnetic field. Ferromagnetic layer 26
as previously stated is typically formed of alloys of one or more
of the following: nickel (Ni), iron (Fe), and cobalt (Co). Magnetic
layer 28 is described as a free ferromagnetic layer. Accordingly,
the magnetic moment of free ferromagnetic layer 28 is not fixed, or
pinned, by exchange coupling, and is free to rotate in the presence
of an applied magnetic field. Free ferromagnetic layer 28 is formed
co-linear with fixed magnetic layer 26 and of alloys of one or more
of the following: nickel (Ni), iron (Fe), and cobalt (Co). Fixed
ferromagnetic layer 26 is described as having a thickness within a
range of 5-500 .ANG.. Free ferromagnetic layer 28 is described as
having a thickness generally in the range of 5-500.ANG..
[0020] In this particular embodiment, spacer layer 16 is formed of
aluminum (Al) and oxygen (O). More particularly, spacer layer 16 is
formed having a general formula of AlO.sub.x, where
O<.times..ltoreq.1.5. It should be understood that when device
10 includes dual spacer layers, as previously discussed, that the
second spacer layer would be formed of oxidized tantalum (Ta),
generally having the formula TaO.sub.x, where
O<.times..ltoreq.2.5.
[0021] Illustrated in FIG. 2, the next step in the method of
fabricating device 10 according to the present invention. More
particularly, as illustrated, the plurality of epitaxially
deposited layers are etched to define device 10 having included as
a part thereof conductive veils 32. Conductive veils 32 are formed
subsequent to ion milling or reactive ion etching which is utilized
to form device 10. Conductive veils 32 provide an electrical path
between first electrode 14 and second electrode 18 and thereby
cause device 10 to fail, due to the shorting out of the device
across insulative spacer layer 16. Typically these veils are etched
off utilizing a wet etch process, which causes degraded device
performance, and thus not suitable for MRAM device fabrication. In
addition, wet etching away conductive veils 32 is hard to utilize
for deep submicron features, results in a non-uniform lateral
over-etch, causing switching fields to vary, and results in an
inability to make every cell the same shape and having the same
switching field.
[0022] Referring now to FIG. 3, illustrated is the next step in the
method of fabricating device 10 according to the present invention.
More particularly, as illustrated, conductive veils 32 are next dry
etched, using oxygen plasma ashing at either room temperature, more
particularly at temperature of 150.degree. C., or a higher
temperature. This oxygen plasma etching of conductive veils 32
provides for the transformation of conductive veils 32 into
insulative veils 34. Insulative veils 34 are thus described as
inactive having non-magnetic, dielectric properties. The
fabrication of insulative veils 32 results in a device having
electrically isolated, first electrode 14 and second electrode
18;
[0023] It should be understood that due to the ability to
electrically isolate first electrode 14 and second electrode 18,
that free magnetic layer 28 can be formed anywhere in device 10.
Prior art dictates the fabrication of the free magnetic layer on
the top of the device stack due to its fabrication as a thin layer,
and the ability to turn portions of it into a dielectric material,
thus electrically isolating the electrodes. This transformation of
the thin free magnetic layer as disclosed and claimed herein
provides for the blocking of the conduction path through the
naturally formed conductive veil between the first electrode and
the second electrode. In this particular invention, in that the
conductive veils have been transformed into insulative veils 34,
free magnetic layer 28 can be formed anywhere in the device stack.
It should be understood that it is anticipated by this disclosure
that device 10 may include a synthetic antiferromagnetic (SAF)
structure that is formed between two tunnel barrier, or spacer,
layers, or alternatively below a first spacer or tunnel barrier
layer, or on a surface of a top spacer or tunnel barrier layer.
[0024] Thus, a magnetic element with insulative veils and
fabricating method thereof is disclosed in which the device
structure and method of fabricating the device is improved based on
the transformation of conductive veils to insulative veils. As
disclosed, this technique can be applied to devices using patterned
magnetic elements, such as magnetic sensors, magnetic recording
heads, magnetic recording media, or the like. Accordingly, such
instances are intended to be covered by this disclosure
* * * * *